Enhanced near-room temperature thermoelectric performance and mechanical strength of n-type BiTeSe materials incorporated with Ag2Se inclusions

Bi2Te3-based alloys are the best thermoelectric materials near room temperature. However, the lower thermoelectric (TE) performance of n-type Bi2Te3-based materials compared to their p-type ones seriously limits the conversion efficiency of thermoelectric devices. In this work, a Bi2Te2.5Se0.5 matrix dispersed with Ag2Se nanoparticles is fabricated. The anisotropic thermoelectric properties of the samples are investigated. A significant increase in electron mobility owing to highly-mobile Ag ions (Ag+) and an increased Seebeck coefficient due to optimized carrier concentration are achieved. Besides, the introduction of Ag2Se nanoparticles results in lowered thermal conductivity due to reduced carrier concentration and enhanced phonon scattering between nanoparticles and phase/grain boundaries. As a result, substantial enhancement of the thermoelectric figure of merit ZT is obtained in both measured directions. In particular, the maximum ZT is 1.12 at 345 K and the average ZT is 1.06 at the measured temperature for the sample BTS-0.15vol%Ag2Se, which is & SIM;62% and & SIM;63% larger than those of the pristine sample, respectively. Moreover, the compression strength of BTS-0.15vol%Ag2Se is four fold as high as that of a commercial BTS sample. The results demonstrate that our work is an effective strategy for enhancing the TE performance and mechanical properties of n-type Bi2Te3-based materials.